For example, as a general technology when a micropattern is formed on a substrate, there is used such a technology that a resist for masking is formed on the substrate before the resist is developed to have a micropattern shape by a lithography technique, and then an etching process or the like is performed. Such a technology is used to form the circuit pattern of a semiconductor, to form MEMS (Micro Electro Mechanical Systems) and the tracks of a recording medium such as an optical disc.
Recently, there has been developed a technology of etching the substrate more deeply by forming an oxide layer on the substrate and forming the resist on the oxide layer (refer to a patent document 1). In this technology, a two-step etching process is performed; the etching process is performed on the oxide layer with the resist being used as the masking, and the etching process is performed on the substrate with the oxide layer after the etching process being used as the masking. The two-step etching process allows the substrate to be etched more deeply than a case where only the resist with the same thickness is used to perform the etching process on the substrate.    Patent document 1: Japanese Patent Application Laying Open NO. She 60-243284